Graph Showing Age by Gender
2000 Census - USA

Census Bureau programs define age as the length of time in completed years that a person has lived. For the most recent decennial census, age was the length of time in completed years that a person had lived as of Census Day--April 1, 2010. The Census Bureau's national surveys compute age as of the interview date.

Focusing on a population's age and sex composition is one of the most basic ways to understand population change over time. In general, the U.S. population continues to grow older with a median age over 40 years old in many states. At the same time, increases in the number of men at older ages are apparent. Understanding a population's age and sex composition yields insights into changing phenomena and highlights future social and economic challenges.